I’m using home-manager to configure my gpg/gpg-agent, and I’m a bit occupied, so I’m not sure I can commit to that. However…
I simplified my gpg config (mostly cleaning un-used cruft from ages ago when I was testing various combos of scdaemon / pscslite / disable-ccid) in the meantime, re-tested, and pushed.
NOTE: At one point in time I was also convinced that it was important to restart the systemd user services for gpg-agent*, for example after killing gpg-agent by hand, rather than letting gpg naively trigger it to startup. I still have a (not-cleaned-up) fix-gpg script that does that.
This the current version that works for me:
https://github.com/colemickens/nixcfg/blob/52e6f2600b1f01dbd223652849caa32d9a4ef42e/mixins/gpg-agent.nix